This invention relates to an improved freezing apparatus and more particularly to a plate type freezing apparatus and method of using this apparatus in a continuous manner for freezing liquid in the form of a sheet or slab that is pure and free from air bubbles and needles and then fragmenting the frozen sheet into fragments as it is harvested.
In many businesses, ice is required in the form of fragments and this fragmented form is preferred to other forms such as cubes or crushed ice. It is a preferred object of this invention to provide an improved apparatus and method of using this apparatus for freezing water into sheets of ice and breaking the sheets of ice into fragments form.
Ice in fragments of varying thicknesses has a variety of uses in industry. One use is for the icing of fishing boats during which fishing boats take aboard ice, preferably in fragmented form to cool the fish catch at sea. Depending on size, boats will take on from 1 to 60 tons of fragmented ice at one loading, and the fish boat icing stations vary in size to suit the needs of the local fishing fleet. Another use for fragmented ice is in poultry processing plants in chill tanks to remove rapidly the body heat from the fowl. A further use for fragmented ice is in the cooling of concrete batches for large concrete structures such as dams, tunnels and heavy earth retaining walls. In some chemical processes, there is a need for fragmented ice for batch cooling and some processes have requirements of up to 100 tons per day. Still other uses of fragmented ice include catering truck icing, sausage making, railway car and field truck icing and some distribution as cocktail ice due to fragmented ice having a lower production cost than cubes.
Automatic ice making apparatus involving reversible cycle refrigeration systems for producing fragmented ice are currently in wide commercial use. In such systems, ice is produced during the normal refrigerating or freezing phase of the apparatus when condensed liquid refrigerant is admitted to the evaporator or evaporator assembly, and the ice is discharged from the evaporator during the defrosting or harvesting phase when hot gaseous refrigerant is delivered directly from the compressor to the evaporator. Some systems have customarily involved an evaporator with a refrigerant chamber having a large volume of liquid refrigerant at the conclusion of the freezing cycle, and one approach has involved rapidly dumping substantially all of the liquid refrigerant from the evaporator into a storage unit at the commencement of the harvesting cycle while introducing the hot gaseous refrigerant in a manner to avoid melting of the ice while achieving release of the frost bond between the ice and the ice-forming or freezing surfaces of the evaporator.
Another system described in U.S. Pat. No. 3,280,585 avoids the dumping or storing of the liquid refrigerant remaining in the evaporator at the conclusion of the freezing cycle by introducing the hot gaseous refrigerant into the refrigerant chamber of the evaporator so that the hot gaseous refrigerant is placed in effective thermal exchange relation with the liquid refrigerant throughout the entire height of the body of liquid refrigerant. This quickly vaporizes the liquid refrigerant or warms it sufficiently to release the frost bond holding the ice to the ice-forming surfaces of the evaporator. This patent uses a simple and effective method of producing and harvesting ice by utilizing a flooded evaporator principle in which no expansion valve is incorporated in the high pressure side of the system and in which no refrigerant is added to the evaporator during the freezing cycle. This patent has an evaporator structure upon which the ice is formed. This ice making apparatus delivers the water to be converted to ice by a water spray header above the evaporator with a pair of parallel horizontal header pipes having upwardly directed spray nozzles for delivering the water in the form of a spray to the large planiform surfaces of the evaporator. The harvested ice from the apparatus of this patent is received in an ice crusher and conveyor assembly operating on the conveyor screw principle, and this crushes the sheet ice discharged from the evaporator.
Another freezing apparatus for freezing liquid is described in U.S. Pat. No. 2,826,045 having at least one freezing plate with a freezing channel, and the plate is generally inclined from the vertical. Means in the form of a liquid distribution unit or pipe having a slit-like nozzle delivers a stream of liquid to be frozen at periodic intervals into the intake end of the channel. A tank is disposed adjacent the discharge end of the channel for recovering any liquid discharged from the channel, and the tank is adapted to be removed from adjacent to the discharge end of the channel at predetermined intervals. A belt is provided so that when the tank is removed from being adjacent to the discharge end of the channel during harvest, the frozen cakes fall from the freezing plates onto the belt which conveys the cakes to a hopper.
It has remained desirable to have a freezing apparatus that utilizes a minimum of energy in the production of fragmented frozen liquids, particularly fragmented ice. In particular it is desirable to eliminate the use of mechanical means to fragment the frozen liquid since this involves the use of energy and the potential of a mechanical failure with the resulting loss of production time during repairs. It is also desirable to have a freezing apparatus that does not use spray means or nozzles for delivery of the liquid since spray nozzles are subject to plugging with particulate matter in the liquid delivery line or in the nozzle with the resulting loss of time and production during unplugging of the line or nozzles. Also the use of spray nozzles can result in the splashing of liquid to areas adjacent the evaporator assembly and this can result in wetting and freezing together of the frozen liquid fragments being harvested when splashed liquid contacts the harvested fragments. It is also desirable to have instrumentation controlling the thickness and the hardness of the frozen liquid sheet. It is also desirable to have a freezing apparatus and associated handling equipment that is completely sanitary for use with food products and constructed to be safe for operating personnel.